logging 模块：记录日志
logging 模块可以用来记录日志：
In [1]:
import logging
logging 的日志类型有以下几种：
logging.critical(msg)logging.error(msg)logging.warning(msg)logging.info(msg)logging.debug(msg)
级别排序为：CRITICAL > ERROR > WARNING > INFO > DEBUG > NOTSET
默认情况下，logging 的日志级别为 WARNING，只有不低于 WARNING 级别的日志才会显示在命令行。
In [2]:
logging.critical('This is critical message')
logging.error('This is error message')
logging.warning('This is warning message')
# 不会显示
logging.info('This is info message')
logging.debug('This is debug message')
CRITICAL:root:This is critical message
ERROR:root:This is error message
WARNING:root:This is warning message
可以这样修改默认的日志级别：
In [3]:
logging.root.setLevel(level=logging.INFO)
logging.info('This is info message')
INFO:root:This is info message
可以通过 logging.basicConfig() 函数来改变默认的日志显示方式：
In [4]:
logging.basicConfig(format='%(asctime)s: %(levelname)s: %(message)s')
logger = logging.getLogger("this program")
logger.critical('This is critical message')
CRITICAL:this program:This is critical message
